Base gasket
 

I was looking over my new 07 EC300 and noticed it has two base gaskets.

Why?

You can adjust the compression ratio/cylinder pressure by varying base gasket thickness (assuming a constant piston dome to pin height). The more gaskets, the lower the compression ratio. It is easier to add/subtract base gaskets than to actually vary cylinder height.

GasGas and other manufacturers sell base gaskets in different thickness so you can "mix and match" and get the correct compression ratio.

The squish is set up conservative like this for different fuels around the world. Generally at the first top end I use a single .3mm. There are .3mm, .5mm, and .15mm(to be used along with a .3 or .5mm). As you know a thinner gasket brings comp up slightly and alters port timing slightly. No X and Y worries like a KTM. To get the most out of the motor you can go with a single .3mm and have the head cut to adjust squish and compression based on that gasket, and the fuel of choice.

My bike has been running particularly good lately on the .15mm gasket coated with some sealer.

Previously I had been running the .3 by itself.

Paul B

Pump gas ? I'm gonna do my top end soon and was planning to stick with .3mm but now you've got me thinking. What sealer do you use ?

Usually 91 or 92 octane. I normal don't use a sealer, but I bought some for the thin gasket. It is Permatex High Tack Gasket Sealant #80062. I have run the bike a couple hundres miles like this and it runs great. I also added an 06 pipe to the bike and the fresh top end so of course it is going to run better regardless of gasket. I found a thread here or on the Smackover site with a report of someone else having luck with it.

Paul B

bead
 

About how big of a bead did you apply?

I coated the entire surface except a thin band on the inner edge. It kind of went on like rubber cement andthe jug sqished just a bit out the sides. It did a nice job sealing up one of my head studs taht had been weeping as well. I actually pulled the topend after install to double check that my rings were both facing the right direction, one ended up being upside down. Live and learn. Most of the sealant had soaked into the gasket which seemed like a good thing.

Paul B

I just realized that I got different gaskets than on my bike. What color is the .3 gasket?

My bike currently has a green gasket and a thicker black gasket. When I order my piston, etc. I ended up with the green gasket and a really thin gasket that is like a piece of brown paper.

I stopped putting my bike back together at that point until I make sure I'm not going to slam the piston into the head.

I ran with the thin one for a while. Had a tiny leak around a stud but no piston touching and no detonation but your mileage may vary.